1. Field of the Invention
The present invention relates to filter unit panels used mainly in inlets of, for example, clean rooms, air conditioning equipment, gas turbines, and steam turbines, and to filter units constituting the same.
2. Background of the Invention
An air filter is provided in each inlet of, for example, clean rooms, air conditioning equipment, gas turbines, and steam turbines. For this air filter, a filter unit panel is used that is formed as an air filter by joining a plurality of filter units together, each of which has a filter medium and a frame for supporting it, with their outer peripheral surfaces being in contact with each other.
JP 2005-177641 A discloses, as an example of the filter unit, “a filter unit comprising a filter medium including a polytetrafluoroethylene porous membrane and an air-permeable fibrous material, and a supporting frame containing resin, wherein the filter medium and the supporting frame are integrated together, with the peripheral part of the filter medium being buried in the supporting frame and the resin permeating the peripheral part”. Furthermore, it also discloses a filter unit assembly in which a plurality of filter units, each of which is the above-mentioned filter unit provided with fitting portions, are joined together by a fitting method of, for example, a hook type or a slide type.
However, the use of the fitting method of, for example, a hook type or a slide type alone as described in JP 2005-177641 A may possibly allow the filter units to slide with respect to each other in a certain direction at the joining portions. Accordingly, the filter units may be movable with respect to each other at the joining portions and are not fixed together satisfactorily, which has been a problem. Furthermore, it is difficult to fit them to each other strictly without forming any gaps at the joining portions. Therefore air can leak through a gap formed at the joining portions although the amount thereof is not large. The air leakage through the joining portions allows particulate in the air also to leak and therefore is a problem particularly in the use of the filter unit assembly for clean rooms where a high degree of dust prevention is required.